1. Field of the Invention
The present invention relates to technologies for detecting a curvature of a road on which vehicles travels.
2. Description of the Related Art
For example, patent document 1, Japanese laid open publication No. 2005-300294 discloses a device and method of detecting a gradient of a road (or a slope of a road), on which a vehicle travels, on the basis of a front scene image of the road in front of the vehicle captured by an in-vehicle monocular camera. The device disclosed in the patent document 1 detects a shape of a lane boundary line on the road on the basis of edge points which have been extracted from the captured front scene image, and detects a gradient of the road on the basis of the detected shape of the lane boundary line.
There is known another conventional device to detect a curvature of the road on the basis of the front scene image of the road captured by the in-vehicle monocular camera. This conventional device detects a shape of a lane boundary line on the basis of edge points extracted from the captured front scene image, and detect the curvature of the road on the basis of the detected shape of the lane boundary line.
However, the shape of the lane boundary line often varies in the captured front scene image due to a gradient of the road. Accordingly, there is a possible difficulty for the conventional device to correctly detect whether the shape variation of the lane boundary line is due to the shape variation of the lane boundary line or the curvature variation of the road. This case reduces the detection accuracy of calculating a correct curvature of the road.